Method of accelerating wound healing by use of interacting metallic sutures



United States Patent 3,477,436 METHOD OF ACCELERATING WOUND HEALING BY USE OF INTERACTING METALLIC SUTURES Philip N. Sawyer, Brooklyn, N.Y., assignor, by mesne ,assignments, to Research Corporation, New York, N.Y.,

a New York non-profit corporation No Drawing. Filed Mar. 11, 1966, Ser. No. 533,451 Int. Cl. A611 17/00; A61b 17/08 US. Cl. 128-3355 3 Claims ABSTRACT OF THE DISCLOSURE A wound closure method is disclosed in which the wound is closed by an aluminum suture which reacts with the tissues to accelerate healing. The acceleration of healing is particularly enhanced in the case of contralateral incisions by utilizing an aluminum suture wire to close one of the incisons and a second suture wire of stainless steel or other material different from aluminum for closing the contralateral incision.

This invention relates to sutures and more particularly to the use of sutures in which the suture material is effective to accelerate the healing of wounds.

The present invention is particularly well suited for sutures of the nonabsorable type, that is, sutures which remain inert and are not absorbed by the body tissues, as opposed to sutures such as catgut, for example, which are absorbed in the tissues. The sutures should be reason ably strong, highly flexible and in many cases should exhibit good electrical conductivity. In addition, they should be devoid of cytotoxic effects, including necrosis, hyperemia and other deleterious reactions produced in the wounds.

Sutures also should be effective to promote the healing of wounds, and it is of course desirable that the tensile strength across the incision or cut be restored to its initial value in a minimum amount of time. Most sutures presently being used comprise monofilament or multifilament strands of silk, catgut or other animal materials, stainless steel, cotton, synthetics, such as nylon, etc. These sutures are used to close the wound and to provide a mechanical holding action until the normal healing process of the body tissues develops suflicient strength to prevent wound disruption. The materials from which such sutures are fabricated, however, have not been shown to actively accelerate or promote the healing of the wound, with the result that there is a distinct possibility of wound separation for comparatively long periods after the wound is sutured.

One general object of this invention, therefore, is to provide a new use for sutures having material therein accelerating the healing of wounds.

More specifically, it is an object of the invention to provide a suture in which the suture material itself is effectiveto accelerate the wound healing process.

Another object of the invention is to provide a suture of the character indicated in which the material from which the suture is fabricated produces an electrical or chemical action which promotes the healing of wounds.

The foregoing and other objects and advantages of the present invention will become more fully apparent from the following description of certain preferred embodiments.

In accordance with the invention, there is provided a suture for accelerating the healing of a wound in human or animal body tissues which is fabricated at least in part from a pure metal which 'has low toxicity and is above the hydrogen ion in the electromotive series. As used herein and in the appended claims, the term pure refers to a metal having a degree of purity commensurate ice 2 with ordinary commercial refining techniques presently in use, as opposed to alloys or other metals in which a substance having different properties is intentionally introduced.

One suture material in this group which is of particular utility is pure aluminum. In addition to the mechanical action of aluminum sutures in closing the wound, the aluminum produces a substantial increase in the rate of healing, resulting in an exceptionally high wound tensile strength across the wound when compared to wounds sutured with more conventional sutures. As an illustration, upon the removal of the aluminum suture one week after the wound is made the tensile strength may be over of the tensile strength of wounds sutured with conventional silk sutures. The aluminum ions react with the tissues of the wound and are believed to play a significant part in the hydroxylation of proline, which is an important process in collagen biosynthesis. The improved biosynthesis of collagen provides a markedly accelerated rate of healing of the wound.

In another illustrative embodiment of the invention, contralateral incisions are sutured with pure aluminum and stainless steel sutures. Wounds sutured with aluminum under these conditions exhibit an even further increase in tensile strength, and in many cases the tensile strength after one week may be more than 200% of the tensile strength of wounds in which conventional silk sutures are used. It is believed that this surprising increase in tensile strength is related to an electrochemical or electromotive interaction between the aluminum and the stainless steel, as well as between the aluminum and the body tissues surrounding the wound.

Aluminum sutures have adequate strength for many surgical operations and are highly flexible. This latter characteristic is particularly desirable to facilitate the tying of knots, including the surgeons knot, without adversely affecting the strength of the suture. As illustrations of representative uses for aluminum sutures, they may be employed in intestinal anastomoses, in the repair of hernia closure of abdominal fascia after laparatomy, and in areas where earlier fibroplasia and higher Wound tensile strength are desirable. Because of aluminums good electrical conductivity, it is readily usable as a suture material in certain types of heart surgery and in other situations in which an electrical impulse is to be applied through the suture to a specific area of the body, or in cases where an external potential is to be established between the suture and the surrounding tissue. In addition, aluminum possesses antiseptic properties which effectively prevent stitch abcess formation.

The biological eifects of aluminum and other nontoxic metals high in the electromotive series are related to several physical and chemical factors. The greater number of metal ions which are released results in an increased rate of dissolution of the metal to produce a correspondingly accelerated rate of healing of the wound. A comparatively high interfacial potential is developed between the metal and the tissues to form an electrolytic effect which, in the case of certain ions, helps to catalyze the healing process. Also, aluminum dissolved in the tissues may act as a protein precipitant on the surface of the fibroblast and increase the polymerization of monomeric particles of tropocollagen. Other chemical effects that are involved may be due to the incorporation of the aluminum ion in the hydroxylation of lysine into hydroxylysine. It is believed that these and possibly other factors combine to further promote the stimulatory action of the aluminum ion on the wound healing process.

Certain metals which are high in the electromotive series produce an adverse effect on the tensile strength of wounds because they are highly toxic. Pure nickel and cobalt, for example, result in a marked necrotic reaction which makes these materials unsuitable for use as sutures. It is an important characteristic of sutures in accordance with the invention that they exhibit low toxicity with minimum adverse tissue reaction.

Metals used as suture materials which are below the hydrogen ion in the electromotive series are not particularlyeffective in accelerating the healing of wounds. As illustrations, pure silver and platinum do not produce any measurable increase in the rate of healing. The effectiveness of copper as a suture material is further minimized because of its severe cytotoxic characteristics which are similar to those of nickel and cobalt.

In tests conducted for experimental purposes to evaluate the effectiveness of various suture materials, eightyone female rabbits having an average weight of 2850 grams were divided into nine groups. The animals were anesthetized with intravenous sodium pentobarbital, and a median skin incision was made in the abdomen of each animal from a few centimeters below the xyphoid to a point above the pubis. The subcutaneous tissue was dissected bilaterally. Two vertical pararectus laparotomy incisions were then made parallel to the midline, this type of incision being chosenbecause, although for certain applications it has decided advantages, in the abdominal structure of rabbits its predisposition to dehisce results in a severe test of the healing capabilities of the wound and the suture. Each incision was ten centimeters long, and the incisions in each animal were spaced 3 centimeters apart. The incisions were closed with continuous sterilized sutures of a size which conformed to United States Pharmacopeia Designation 30. The sutures were of different materials but were otherwise identical and were placed 5 millimeters from the edge of the incisions with 5 millimeters between loops. The skin was closed with continuous 20 silk sutures.

On the seventh postoperative day, the skin of each animal was reflected and the wound examined. Measurethe sutures and the wound tissues was 360 millivolts. The strips which had been sutured with silk showed a mean tensile strength of 300 grams, and there was no measurable interfacial potential. The tensile strength of aluminum sutured wounds at seven days was thus approximately 143 percent of the silk control.

The histological study revealed that there was a definite increase in collagen fibers visible under a microscope in wounds sutured with aluminum when compared with the silk sutured wounds. The improved bio'synthesis of-collagen is believed to be directly attributable to' the use of aluminum. The observed inflammatory reaction of the aluminum was close to that of silk and was within acceptable limits.

EXAMPLE II The incisions in another group containing five animals were closed with aluminum sutures on one side and stainless steel sutures on the contralateral side. The mean tensile strength of the wounds sutured with aluminum was 724 grams, or approximately 240 percent of the tensile strength of the silk control. The interfacial potential between the aluminum and the tissues was again observed to be 360 millivolts. It is believed that the substantially increased tensile strength resulted from an electrochemical or electromotive reaction between the aluminum and the stainless steel, as well as from the reaction between the aluminum and the tissues, making more aluminum ions available to the healing tissue. A marked increase in collagen fibers was readily apparent under the microscope, and the inflammatory reaction was about the same as in Example I.

The incisions in the remaining six groups of animals were closed with sutures made from platinum, silver, co per, nickel, cobalt and stainless steel. The results of the series of experiments are summarized in the following table:

Mean Tensile Tensile Strength Strength Compared of Wound Interfacial to Silk Number Strips Potential in Control,

Suture Material of Animals in Grams Millivolts Percent Aluminum (stainless steel used eontralaterally) 5 724 +360 241 Aluminum. 10 431 +360 143 Silk 11 300 0 100 Platinum 9 254 140 84 Silver. 8 293 -80 87 Copper 10 147 +40 49 Niekel 8 220 +20 74 Cobalt 10 281 +30 71 Stainless steel 10 334 110 ments were made of the spontaneous electrical potential generated between the suture wire and the muscle tissue adjacent the wound. The sutures were then removed, and the anterior abdominal wall was dissected and divided transversely into eight equal strips which each had a width of 1 centimeter and extended across both sides of the wound. One strip from each animal was used for histological study, and the remaining strips were divided at the midline to separate the two laparatomy incisions and thus provide fourteen test specimens from each animal. The tensile strength of these specimens was measured using a motor tensiometer.

EXAMPLE I In one group of ten animals, sutures of pure aluminum were employed bilaterally, while in another group of eleven animals silk sutures were similarly used for purposes of control. The mean tensile strength of the 140 test strips in which aluminum had been used was 431 grams, and the developed intcrfacial potential between A market necrotic reaction was observed in the wounds sutured with nickel, cobalt and copper, the muscletissues sutured with these wires displayed gross nercrosis surrounding the wire, hyperernia and local vascular engorgement with thrombosis. The necrosis of muscle tissue produced by nickel and cobalt was white and grumous, while that produced by copper resulted in a green discoloration. These metals in their pure state are not believed to be suitable for use as sutures.

EXAMPLE III incisions were closed using continuous 3-0 pure aluminum sutures on one side and 30 silk sutures as controls on the contralateral side. The sutures were placed five millimeters from the edge of the wound with 5 millimeters between each loop. The skin was closed with continuous 2-0 silk sutures.

The sutures were removed from the animals in the respective groups on the3rd, 5th, 7th, 10th, 14th, 21st, 28th and 56th postoperative days. The anterior abdominal musculoperitoneal wall of each animal was dissected out and divided into ten equal strips one centimeter wide. Eight of these strips were-separated at the midline to provide eight specimens per animal of incisions sutured with aluminum and a corresponding number of contralateral incision specimens sutured with silk. The mean tensile strength of the aluminum'f'sutured wounds in each group was compared with the contralateral silk sutured control,

giving the following results:

Mean Mean Tensile Tensile Strength Strength of of Aluminum Silk Sutured Sutured Number Wounds Wounds m 1n Animals Grams Grams It is apparent from the foregoing table that the wounds sutured with aluminum were consistently stronger than wounds sutured with silk; After the first three days, the tensile strength of the silk sutured wounds did not approach that of the aluminum sutured wounds until eight to ten weeks had passed. The aluminum sutured wounds at seven days were approximately 30% as strong as nonincised normal muscle strips, while the silk control wounds were only about as strong.

The foregoing examples have been given in order to more clearly disclose thenature of the present invention. It should be understood, however, that this has been done solely by way of example and is intended neither to delineate the scope of the invention nor limit the ambit of the appended claims.

Athough the use of a pure metal above the hydrogen ion in the electromotive series as a suture material to accelerate the healing of wounds has many important advantages, in some embodiments of the invention a metal such as aluminum may be combined with other materials to form sutures which produce the desired results. In addition, the pure metal may be stranded with materials such as stainless steel, for example, or may be used as a coating on either metallic or non-metallic sutures. In these latter embodiments, the coating is in the form of an exposed pure metal surface which reacts with the body to promote wound healing.

Sutures constructed in accordance with the invention may be made in accordance with substantially any of processes commonly used for the manufacture of sutures. In several preferred embodiments, the sutures comprise mono-filament untwisted wires of the appropriate metal. In other cases, they may be braided, twisted or otherwise fabricated in accordance with known manufacturing techniques. 1

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features described, or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. In a method of promoting healing in a wound having contralateral surgical incisions, the steps of closing one of said incisions with a suture fabricated at least in part from aluminum, and closing the contralateral incision with a suture fabricated from a nontoxic material different from aluminum, said diiferent. material being capable of interacting with aluminum and being above the hydrogen ion in the electromotive series, ;said aluminum cooperating and reacting with said different material and with the tissues of the wound to accelerate wound healing.

2. t In a method of promoting healing in a wound having contralateral surgical incisions, the steps of closing one of said incisions with a suture fabricated from aluminum metal, and closing the contralateral incision with a suture fabricated from stainless steel, said aluminum cooperating and reacting with said stainless steel and with the tissues of the wound to accelerate Wound healing.

3..- In a method of the character set forth in claim 2, in which said one incision is closed with a suture fabricated substantially entirely from pure aluminum.

References Cited UNITED STATES PATENTS OTHER REFERENCES Handbook of Ligatures & Sutures (Johnson & Johnson), 3d edit., 1931, pp. 8-9 relied on.

Andrews: J.A.M.A., July 28, 1917, pp. 278-281.

Kraissl: International Abstracts of Surgery, May 1936, pp. 417-423.

DALTON L. TRULUCK, Primary Examiner 

